Maternal provisioning of offspring and the use of those resources during ontogeny: variation within and between Atlantic Salmon families

Summary

• 1
   The size and proximate composition of eggs and alevins (larvae) were measured from six full sibling families of Atlantic Salmon (Salmo salar), at six stages between fertilization and first feeding.
• 2
   Egg and alevin size measures (diameter, wet mass, dry mass) and proximate composition attributes (water, protein, fat, energy) were all highly correlated with each other (r = 0·89–0·99), suggesting that each is a reasonable surrogate for any other.
• 3
   Most of the variation in egg size (95·0–97·0%) and composition attributes (95·5–97·9%) was partitioned between, rather than within, females. Most of this variation was attributable to differences in female size, owing to the length of time spent at sea.
• 4
   Fat, protein and energy content varied less on a relative basis (controlling for egg size variation) than on an absolute basis, suggesting that certain combinations of egg attributes are optimal regardless of egg size.
• 5
   Stored fat decreased by 9·6 µg day⁻¹ before hatching but increased by 27·4 µg day⁻¹ after hatching. The increase after hatching suggests that alevins actively synthesize (probably from protein) and store lipids between hatching and first feeding.
• 6
   Stored protein decreased by 8·8 µg day⁻¹ before hatching and by 181·3 µg day⁻¹ after hatching. Assuming all metabolic energy was derived from stored protein, metabolic rate increased logarithmically from 0·115 J day⁻¹ to 5·43 J day⁻¹. Rates of oxygen consumption estimated from protein loss (6·09–288·9 µl O₂ d⁻¹) were similar to those reported in studies that measured oxygen consumption using respirometry.
• 7
   Alevins appear to convert protein to fat, a change that their mothers were unable or unwilling (in an evolutionary sense) to make. This may reflect the conflicting goals of parents and offspring for maximizing fitness.